This invention is generally in the area of the use of microchannel reactors and/or combinatorial chemistry to optimize the conditions for endo- and exothermic catalytic reactions.
Combinatorial chemistry is in widespread use in the pharmaceutical industry, where it is used to synthesize, purify and evaluate new drugs at a tremendously fast pace. In the field of pharmaceutical chemistry, the reactions are typically performed at a relatively small scale, since only a small amount of each drug is required for testing. Typically, only those drugs which are active in relevant bioassays are scaled up. The type of chemistry used to generate commercial quantities of the drugs is rarely the same as that used in small scale synthesis.
Combinatorial chemistry is also being used in petroleum chemistry. However, a major goal in petroleum chemistry is to optimize the reaction conditions and catalysts used for particular reactions rather than to synthesize, purify and evaluate a plurality of products. To have commercial significance, there must be a correlation between the results obtained on the small scale and those which might be obtained on a commercial scale.
One combinatorial chemistry approach used by Symyx to identify optimum catalysts for various reactions involves placing a plurality of catalysts on a metal plate, contacting the plate with a gaseous reactant, and analyzing the products obtained via GC/MS. This approach is limited because, at least for a number of exothermic and endothermic catalytic reactions, it is difficult to correlate the results obtained on this small scale with those obtained on a commercial scale. This limitation exists, in part, because the heat transfer obtained on such a small scale cannot reasonably be correlated with what would be observed in a large reactor.
Heat transfer effects are extremely relevant in exothermic and endothermic reactions. For example, Fischer-Tropsch synthesis, an exothermic reaction, is very sensitive to heat transfer effects. A small scale reaction which provides an acceptable product mixture may provide an unacceptable level of methane production on scale-up due to heat transfer effects. Accordingly, it is often difficult to extrapolate the results on small scale endo- and exothermic reactions to commercial scale reactors. However, it is also difficult to perform combinatorial chemistry using commercial scale reactors.
It would be advantageous to provide devices and methods for discovering optimum catalyst systems using combinatorial chemistry that take the heat transfer effects on product distribution into consideration. The present invention provides such devices and methods.
The present invention is directed to devices and methods for optimizing endo- and exothermic reactions, in particular, gas-to-liquid reactions, using combinatorial chemistry. The devices include a microchannel reactor that includes a plurality of channels. Some or all of these channels are used to carry out the desired endo- or exothermic reactions. The individual channels include individual catalysts or combinations thereof, such that all or part of a combinatorial library of catalysts can be evaluated. The devices can also include channels which are used to provide heating and cooling, and/or heating and cooling can be provided using other means.
The methods use a combinatorial approach to identify optimum reaction conditions and catalysts or catalyst combinations for performing the desired reactions and/or for providing a desired product. Preferred exothermic reactions are gas-to-liquid reactions, in particular Fischer-Tropsch synthesis, isosynthesis, olefin oligomerization, olefin polymerization, and syngas generation by partial oxidation, methanol synthesis, oxidative methane coupling to ethane and ethylene, methanol conversion to hydrocarbons. Preferred endothermic reactions are catalytic cracking, naphtha reforming, methane conversion to aromatics and steam reforming of methane; steam reforming reaction of H2O with CH4 to make H2 and CO, with traces of CO2; aromatization, the conversion of paraffins and olefins to aromatics, and hydrocracking reactions. The products can include olefins such as ethylene, iso-paraffins, aromatics and combinations thereof, and preferably include iso-paraffins in the distillate fuel and/or lube base stock ranges, and, more preferably, iso-paraffins in the jet or diesel range.
The methods involve obtaining a microchannel device that includes a plurality of channels, placing an effective amount of a catalyst (or a catalyst combination) from one or more catalyst libraries in a channel, repeating this step as necessary with different channels and different catalysts, and performing the desired reactions. The product streams are preferably analyzed, for example by GC, HPLC and/or GC/MS. The reaction conditions, catalysts, and analytical information regarding the product streams are preferably stored in a database.
The information obtained in the combinatorial step can be applied commercially in several ways. For example, a plurality of microchannel reactors can be used in series and/or in parallel such that the chemistry can be performed on a commercial scale in the plurality of microchannel reactors. This is advantageous, since the reaction conditions and catalysts used in the combinatorial step are directly applicable to the commercial scale chemistry. Alternatively, the results obtained in the microchannel reactors can be correlated to what would be obtained in a conventional large scale reactor.
The microchannel reactors are preferably in the form of a microcomponent sheet architecture, for example a laminate with microchannels. The sheet architecture may be a single laminate with a plurality of separate microcomponent sections or the sheet architecture may be a plurality of laminates with one or more microcomponent sections on each laminate. The microcomponents include passive microcomponents, for example micro flow paths, and active components including but not limited to micropumps and microcompressors. In one embodiment, one type of laminate receives chemical reactants, rejects chemical products and rejects or receives heat to or from a second type of laminate.
The microcomponents or plurality of like microcomponents can perform at least one unit operation. In one embodiment, a first laminate having a plurality of like first microcomponents is combined with at least a second laminate having a plurality of like second microcomponents. The combination of at least two unit operations provides a system operation. For example, a laminate containing a plurality of microchannel evaporators can be combined with an insulating laminate and a laminate containing a plurality of microchannel condensers, and connected to a compressor and expansion valve to obtain a macroscale heat pump. The laminates can be used for chemical processes such as chemical conversions and separations.
Heat transfer in the microchannel reactors is controllable, in part by adjusting the heating/cooling through the microchannels, through the individual laminate layers, and/or through the judicious choice of materials used to prepare the reactors. Ideally, the heating and/or cooling provided by the microchannel reactors can be made to approximate or at least be correlated to that of a large scale (commercial) reactor. One way to provide such a correlation is to place a commercially-known catalyst in one or more of the channels, and adjust the reaction conditions/heating/cooling and other factors such that the results can be correlated with the results obtained in the large scale commercial reactors.
Whether the results obtained in the combinatorial step are used in a plurality of microchannel reactors, or the chemistry is scaled up to a large scale reactor, it may be advantageous to include the same catalyst in a plurality of channels to verify that the results obtained are reasonably consistent throughout the reactor.
The methods can advantageously be used to generate a database of catalysts and, optionally, reaction conditions, which provide various product streams. As market conditions vary and/or product requirements change, conditions suitable for forming desired products can be identified with little or no downtime using the methods described herein.